Induction and identification of artificial triploid fry in Cynoglossus semilaevis

Half-smooth tongue sole(Cynoglossus semilaevis) is a newly exploited and commercially important cultured marine fish in China.Females grow 3-4 times faster than males.Thus,the development of all-triploid stock would be of significant benefit for aquaculture.In the present study,a set of experiments were carried out for developing artificial all-triploids technique in the tongue sole.First of all,and the optimal initiation time for pressure shock of fertilized eggs was determined to be 5 min after fertilization when the fertilized eggs were incubated at water temperature of about 23 ℃,the optimal pressure and treatment duration were determined to be 36 MPa and 4 min,respectively.Ploidy of fry was analyzed using Ploidy analyzer.Under the optimal induction conditions,100% triploids were obtained.63 chromosomes were observed in artificial triploid fry and,42 chromosomes were observed in normal diploid fry.Thus,a set of techniques for induction of triploid fry was developed for the first time in half-smooth tongue sole,and 100% triploid fry were obtained.This technique lays foundation and provides important tool for sex control and production of high quality seeds in half-smooth tongue sole.